Traditional material handling systems often utilize conveyor devices configured to transport substantial amount of material. Examples of material handling systems that utilize conveyor devices may be appreciated from U.S. Pat. Nos. 7,191,888, 6,782,993, 6,155,400, 6,085,890, 5,609,397, 5,562,194, 5,090,549, 4,139,087, 3,604,757, 2,851,150 and 1,996,488, and U.S. Patent Application Publication Nos. 2011/0132719, 2010/0314214, 2010/0288603, and 2007/0102263.
Conveyor systems used for stacking material may include a system configured for using radial stackers and grasshopper conveyors, for example. The radial stacker in such systems is configured to work in a circular path and often has an extendable conveyor head to increase the time between stack moves. The system is set up at an initial location with the stacker at its initial position. Once the radial stacker completes its first rotation, the head of the stacker may be extended or retracted and the stacker could reverse its path to further stack material. This process may continue until the stacker has stacked a distance equal to the extension/retraction length of the extendable conveyor head. The stacker and single section bridge then may index forwards or backwards to a new location to stack additional material.
Movement to the new location often takes a significant amount of time. For instance, the stacker may need to be moved by a lifting device or by towing the stacker. In this type of system, the stacker tail end is often supported by the head end of a single section bridge conveyor. The single section bridge conveyor either pushes or pulls the stacker depending on whether the stacker is advance or retreat stacking. Grasshopper conveyors may be positioned adjacent to the single section bridge conveyor to transfer material to the single section bridge conveyor feeding the stacker. For advance stacking versions of this system, grasshopper conveyors may be added to the system. For retreat stacking versions of this system, grasshopper conveyors may be removed from such a system. Grasshopper conveyor systems are usually only used for retreat stacking.
As the single section bridge conveyor moves, it travels under the discharge of a unique inclined cross conveyor that transports material from a grass hopper conveyor to a bridge conveyor for feeding material to the stacker. Once the bridge conveyor has moved a distance equal to the length of a grasshopper conveyor, the grasshopper conveyor is removed or added for stacking material at another position. Movement of the single section bridge conveyor, inclined cross conveyor, and stacker when adding or removing a grasshopper conveyor usually requires the system to be shut down. Additionally, movement of the grasshopper conveyors for adding or removing grasshopper conveyors typically requires the system to be shut down. Such shut downs require significant costs to be incurred. For instance, the entire material handling process may need to be shut down to accommodate movement of the grasshopper conveyor, stacker and bridge conveyor. The costs associated with such a shut down may range from 50,000 to 150,000 dollars in a mid sized material handling system that may be configured for handling 10,000 to 50,000 tons of material per day
A new material handling system is needed that permits material to be stacked without the need to shut down a material handling operation to accommodate movement of a stacker, section bridge conveyor, or the removal of portable conveyors used to feed material to the stacker. Preferably, such a system is able to be utilized for retreat stacking and permits continuous material throughput throughout the stacking of material into a cell of a storage area. The system also preferably does not require the use of any inclined cross conveyor or other type of cross conveyor for feeding material from a portable conveyor to a bridge conveyor for stacking the material via a stacker.